1. Field of the Invention
The present invention relates to an electron emitter which is configured such that it can emit electrons through application of a predetermined electric field.
2. Description of the Related Art
This type of an electron emitter is configured such that when a predetermined electric field is applied to an electron emission section (emitter section) in a vacuum having a predetermined vacuum level, electrons are emitted from the electron emission section (emitter section).
Such an electron emitter is employed as an electron beam source in various apparatuses that utilize electron beams. Specific examples of such an apparatus include a display (in particular, a field emission display (FED)), an electron beam irradiation apparatus, a light source device, an electronic-component-manufacturing apparatus, and an electronic circuit component.
In application to an FED, a plurality of electron emitters are two-dimensionally arrayed. In addition, a plurality of phosphors corresponding to the electron emitters are arrayed with a predetermined gap therebetween.
In an FED having such a configuration, among the two-dimensionally arrayed electron emitters, certain electron emitters are selectively driven so as to emit electrons therefrom. The emitted electrons collide with phosphors corresponding to the driven electron emitters. The phosphors hit by the electrons fluoresce, thereby providing a display.
Electron beam irradiation apparatuses are employed for, for example, the following applications: solidification of an insulating film during wafer lamination in a semiconductor chip production process; hardening or drying of printing ink; and sterilization of a packaged medical instrument. Electron beam irradiation apparatuses are superior to ultraviolet-ray irradiation apparatuses, which have conventionally been employed for the aforementioned applications, in that high output is easily obtained, and radiated electron beams are absorbed by a target object in a highly efficient manner.
The aforementioned electron emitter is suitable for use in a light source device requiring high brightness and high efficiency. Specific examples of such a light source device include a light source device of a projector. As compared with an ultrahigh-pressure mercury lamp, which has conventionally been employed as such a light source device, a light source device employing the electron emitter is advantageous in that the device can attain miniaturization, long service life, high speed, and reduction of load imposed on the environment. A light source device employing the electron emitter can be employed in place of an LED. Specifically, such a light source device can be employed in, for example, an interior lighting apparatus, an automobile lamp, a traffic signal, or a backlight of a small liquid crystal display for cellular phones. Combination of the electron emitter and a phosphor can form a light-emitting device for exposure of a photosensitive drum of an electrophotographic apparatus.
When the electron emitter is applied to an electronic-component-manufacturing apparatus, the electron emitter is employed in, for example, an electron beam source of a film formation apparatus (e.g., an electron beam deposition apparatus), an electron source for plasma formation (for activation of gas, etc.) in a plasma CVD apparatus, or an electron source for gas decomposition.
Examples of electronic circuit components to which the electron emitter is applied include digital elements such as switches, relays, and diodes; and analog elements such as operational amplifiers. When the electron emitter is applied to such an electronic circuit component, current output can be increased, and amplification factor can be enhanced.
In addition to the aforementioned applications, the electron emitter is employed in, for example, vacuum micro devices such as high-speed switching devices operated at a frequency on the order of tera-Hz, and large-current outputting devices. The electron emitter is also suitable for use as an electron source for charging a dielectric material.
Specific examples of the electron emitter are disclosed in Japanese Patent Application Laid-Open (kokai) Nos. 07-147131, 2000-285801, 2004-146365, 2004-172087, 2005-116232, and 2005-142134.
The electron emission section (emitter section) of the electron emitter disclosed in Japanese Patent Application Laid-Open (kokai) No. 07-147131 or 2000-285801 is formed of a fine conductive electrode having a pointed tip end portion. Such a disclosed electron emitter includes a counter electrode provided so as to face the emitter section. The electron emitter is configured such that when a predetermined drive voltage is applied to the emitter section and the counter electrode, electrons are emitted from the tip end portion of the emitter section.
When the electron emitter disclosed in Japanese Patent Application Laid-Open (kokai) No. 07-147131 or 2000-285801 is to be produced, forming the aforementioned emitter section from such a fine conductive electrode requires micromachining that employs, for example, etching or fine forming (electro fine forming), and thus production of the electron emitter involves a complicated process.
In the electron emitter disclosed in Japanese Patent Application Laid-Open (kokai) No. 07-147131 or 2000-285801, a high level of drive voltage must be applied to the electron emitter for causing a sufficient quantity of electrons to be emitted from the tip end portion of the conductive electrode. Therefore, driving the electron emitter requires an expensive drive element (e.g., IC) which is applicable to high-voltage drive.
Thus, the electron emitter disclosed in Japanese Patent Application Laid-Open (kokai) No. 07-147131 or 2000-285801, which includes an emitter section formed of a conductive electrode, involves a problem in that high cost is required for producing the electron emitter per se, or a device employing the electron emitter.
In order to cope with the problem, there has been devised an electron emitter including an emitter section formed of a dielectric thin layer (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2004-146365, 2004-172087, 2005-116232, or 2005-142134). Hereinafter, such an electron emitter may be referred to as a “dielectric-film-type electron emitter.”
The dielectric-film-type electron emitter disclosed in Japanese Patent Application Laid-Open (kokai) No. 2004-146365, 2004-172087, 2005-116232, or 2005-142134 includes the aforementioned emitter section, a cathode electrode, and an anode electrode. The cathode electrode is formed on the front surface side of the emitter section. The anode electrode is formed on the reverse surface side of the emitter section, or on the front surface side of the emitter section at a position a predetermined distance away from the cathode electrode. Specifically, the dielectric-film-type electron emitter is configured such that an exposed portion of the front surface of the emitter section at which neither the cathode electrode nor the anode electrode is formed is present in the vicinity of a peripheral edge portion of the cathode electrode.
The dielectric-film-type electron emitter is operated as follows.
Firstly, in the first stage, voltage is applied between the cathode electrode and the anode electrode such that the cathode electrode is higher in electric potential. An electric field generated by the applied voltage brings the emitter section (in particular, the aforementioned exposed portion) into a predetermined polarization state.
Subsequently, in the second stage, voltage is applied between the cathode electrode and the anode electrode such that the cathode electrode is lower in electric potential. At this time, electrons are emitted from the peripheral edge portion of the cathode electrode, the polarization of the emitter section is inverted, and the electrons are accumulated on the front surface of the emitter section. When voltage is again applied such that the cathode electrode is higher in electric potential, the polarization of the emitter section is re-inverted, and the thus accumulated electrons are emitted by means of electrostatic repulsion between the electrons and dipoles. The electrons fly in a predetermined direction by means of an externally applied, predetermined electric field; i.e., the dielectric-film-type electron emitter emits electrons.